Patient health care and biological research have made dramatic improvements in recent years, in part due to the utilization of assay techniques. Such assay techniques generally involve reacting a specimen to be assayed, usually a biological solution, e.g., blood, urine, tissue, cell, DNA, RNA, etc., with a magnetically responsive material, e.g., a magnetic containing material or a paramagnetic containing material, in a non-magnetic test media in a specimen container to produce a magnetically responsive complex. A magnetic field is applied or induced in or around the specimen container in order to isolate the magnetically responsive complex from the non-magnetic test media. Thereafter, either the magnetically responsive complex or the non-magnetic test media is withdrawn from the specimen container so that the magnetically responsive complex may be freed from the specimen material. The use of magnetic separation using solution and magnetic particles or complexes is well known in the art of diagnostic assay such as, but not limited to, immunoassay, genetic probe assay, ligand-receptor assay, protein-ligand assay, and hybridization-type assay. Apparatus and methods used to accomplish these types of assays vary from process to process and are well known in the art. The apparatus and methods can be of a non-automated type using a stationary magnet as disclosed in U.S. Pat. Nos. 3,985,649; 4,672,040; 4,695,392; 4,793,973; 4,935,147; 5,145,784; 5,279,936; 5,691,208; or of an automated or of a flow through type as disclosed in U.S. Pat. Nos. 3,970,518; 4,141,687; 4,375,407; 4,738,773; 4,910,148; 5,147,529; 5,318,914; 5,411,863; 5,536,475; 5,541,072; 5,602,042; 5,705,059; 5,711,871; 5,779,907; or of a type using a pin or magnetized means to dip into a container as disclosed in U.S. Pat. Nos. 4,272,510; 4,649,116; 4,751,053; 5,567,326; or of the stationary test tube rack magnetic separation type device with a magnetic member external to the container as disclosed in U.S. Pat. Nos. 5,571,481; 5,108,933; 4,988,618; 4,895,650; 4,438,068; Des. 280,130. The aforementioned U.S. patent disclosures are incorporated herein by reference so as to illustrate the background of the invention and are not, by their inclusion, necessarily conceded to be prior art. The assembly according to the present invention relates to a stationary test tube rack magnetic separation type device with a magnetic member external to specimen containers.
Known stationary test tube rack magnetic separation devices are generally inconveniently sized to accommodate only one size of specimen container (e.g., a vial or a test tube or any single volume container), thereby requiring the extra expense of purchasing additional devices to accommodate different sizes of specimen containers.
Another problem with prior stationary test tube rack magnetic separation type devices concerns decanting the non-magnetic test media from the specimen containers. Many of the prior devices have rows of specimen containers oriented in multi-column, multi-row arrays, thereby preventing removal of the non-magnetic test media by simply decanting the media. The proximity of the rows and columns provides opportunities for cross contamination of the material found within the specimen containers if a simple decanting operation is performed by tipping the devices.
Yet another problem exists in prior devices where the stationary test tube rack magnetic separation devices have a longitudinally slidable magnetic member which slides into and out of a longitudinal bore which is closed at one end (see e.g., U.S. Pat. No. 5,571,481). Should there be any dirt or debris within the bore, the longitudinal member may bind and the magnets in the magnetic member may not properly align with the test tube sidewalls, thereby reducing the accuracy of the assay. In addition, there may be longitudinal slippage or sliding of the device as the longitudinally slidable member is aligned with and longitudinally inserted into the longitudinal bore. The slippage may cause interference with the test tubes or the solutions therein.
Still other problems exist in prior devices where the magnets of the stationary test tube rack magnetic separation devices are snap-fitted into place. The action of snapping one or more magnets to the appropriate mechanism may lead to spillage of the samples thereby causing less than accurate results or undesirable contamination. Additionally, when installing one or more magnets in the separation device, it is possible to position the magnet(s) in the wrong orientation which may lead to a poor separation result. Moreover, considering the strength of the magnets typically used in these prior devices, a free or removable magnet may create a hazardous situation. Such magnets, when not properly handled or stored, may tend to attach themselves to undesired hosts thereby possibly causing a multitude of problems as can be appreciated by those skilled in the art.
Another problem with prior stationary test tube rack magnetic separation type devices is the lack of efficient handling of multiple samples during both the mixing and separating operations.